1. Field of the Invention
The present invention relates to a vehicle side, air bag apparatus that inflates and expands a side air bag between an occupant and a vehicle body side portion in the event of a collision of a vehicle etc. and a vehicle seat in which the vehicle side air bag apparatus is mounted.
2. Description of Related Art
In a side air bag apparatus disclosed in Japanese Patent Application Publication No. 2009-241643 (JP 2009-241643 A), an inner side of an air bag is vertically separated to a chest region protection portion and a lumbar region protection portion, and the lumbar region protection portion is further horizontally separated to a first lumbar region protection portion (a first compartment) and a second lumbar region protection portion (a second compartment) in a laminated manner. The first compartment of the lumbar region protection portion and the chest portion protection portion communicate with each other, and gas from a first inflator is supplied to the chest region protection portion via the first compartment. This inflates and expands the entire air bag widely and immediately to protect an occupant from his chest region to his lumbar region on the lateral side. Next, gas from a second inflator is supplied to the independent second compartment of the lumbar region protection portion, so that the lumbar region with tolerance can be stably supported with a sufficient inner pressure.
In this side air bag apparatus, when the air bag inflates and expands, firstly the first compartment of the lumbar region protection portion and the chest region protection portion inflate and expand to smoothly expand the air bag into a narrow space between the lumbar region of the occupant and a vehicle body side portion.
Incidentally, the size of a space between the lumbar region of the occupant and the vehicle body side portion in the event of a side impact significantly differs depending on the form of the side impact. For example, in a case where a local load is inputted to the vehicle body side portion away from the occupant due to a so-called pole side impact etc., since the vehicle body side portion locally intrudes into a vehicle interior, there is a case that a relatively wide space can be secured between the lumbar region of the occupant and the vehicle body side portion. On the other hand, in a case where a collision load is inputted into a relatively large section of the vehicle body side portion as in a so-called MDB barrier side impact for example, since the large section intrudes into a vehicle interior, there is a case that a space between the lumbar region of the occupant and the vehicle body side portion is made narrower.
Consequently, in the above-described side air bag apparatus, when an inflation thickness (bag thickness) of the lumbar region protection portion of the air bag is set, a case where a space between the lumbar region of the occupant and the vehicle body side portion is made narrower should be considered. As a result, it is believed that the inflation thickness (especially, the inflation thickness of a lower end portion) of the lumbar region protection portion is made thinner, which deteriorates the occupant constraint property.
In addition, in the above-described side air bag apparatus, the performance in which an effect provided on the occupant is made smaller even when the air bag inflates and expands in a state that the occupant is positioned in an inappropriate position which is an inflation and expansion region of the air bag (hereinafter, OOP performance) is required. However, in order to improve this OOP performance, lowering an inner pressure of the air bag deteriorates the occupant constraint property.